|n||The upper range from which the random number will be selected.|
This very useful function only returns integers (whole numbers).
So, for example, to get a random number from 0 to 9 you can use
irandom(9) and it will return a number from 0 to 9
inclusive... real numbers can also be used but the upper value will
be excluded, so irandom(9.7) will return a value from 0 to
9 only. The function has an upper bound of $7fffffffffffffffLL, so
care should be taken if using very large numbers.
NOTE: This function will return the same value every time the game is run afresh due to the fact that GameMaker: Studio generates the same initial random seed every time to make debugging code a far easier task. To avoid this behaviour use randomize at the start of your game.
if irandom(9) = 1
score += 100;
This will produce a one in ten (since 0 is included) chance of adding 100 to the score.